Prepayment electricity meter



March 21, 1933.

5. 2. DE FERRANTI PREPAYMENT ELECTRICITY METER Filed Oct. 14, 1931.

Patented Mar. 21, 1933 UNITED STATES PATENT, OFFICE LATE OF HOLLIN WOOD, ENGLAND, BY LEGAL I REPRESENTATIVE, OF LONDON,

YORK, N. Y.

PREPAYMENT ELECTRICITY METER Application filed October 14, 1931, Serial No. 568,839, and in Great Britain september 25, 1930.

This invention relates to electric switches especially for prepayment electricity meters and has for its object to provide improved constructions thereof.

Thefailure of any switch to break a current successfully is due to an arc persisting across the electrodes. Arcing is a condition of intense ionization, and thus any switch which prevents or limits the ionization at the break will give a good performance.

The object of the present invention is to provide improved switches wherein rapid deionization is induced as the current wave passes through zero, the current therefore being unable'to restart during the subsequent half cycle of the voltage wave.

Switches according to the present inven tion are suitable for controlling non-continuous current, e. g., thecurrent supplied for domestic use through alternating current meters.

The present invention mainly consists in an electric switch of considerable currentcarrying capacity including contact members having fiat contacting surfaces adapted to be urged into mutual contact with sufficient pressure to prevent appreciable local temperature rise whilst the switch is closed and adapted to open to a small extent only, whilst the contacting surfaces remain substantially parallel.

Referring to the accompanying diagrammatic drawing which illustrates by way of example one convenient construction in accordance with the present invention:

Figure l is a plan view illustrating the switch combined with prepayment mechanism of an electricity meter;

Figure 2 is a vertical cross-sectional view through the centre line of one of the fixed contacts of Figure 1.

In carrying the invention into effect according to the example illustrated, fixed contacts 19 and 20 are provided placed side by side and adapted to be bridged by a bridge member 21, the mutually contacting surfaces being flat.

The bridge member is urged away from the contracts by a C-shaped spring 23, the plane of the operative surfaces on the bridge piece, however, being maintained parallel with or subsequently parallel with the plane containing the operative surfaces of the fixed contacts throughout the full extent of the opening movement. The extent of the movement provided is about .01 inch.

It will be noted that a considerable surface area is provided for the contacting surfaces of the contacts 19 and 20 and the bridge piece 21. i

In order to overcome the pressure of the C-shaped spring so as to close the switch, toggle mechanism is provided comprising two members 24 and 25 mutually hinged, one end of the member 24 being pivotally attached at 26 to the bridge member 21, whilst one end of the member 25 is pivotaliy attached at 27 to a fixed frame.

A second. toggle mechanism is provided comprising two members 28, 29 mutually pivoted at 18. The upper end of the member 28 is pivotally connected at 61 to the centre of the toggles 24, 25, whilst the lower end of the member 29 is pivotally attached at 29a to the said frame. The upper member 28 of this latterv toggle mechanism is extended downwards in order to reduce the tripping pressure necessary, which latter is applied by the bell crank lever 33a.

I In operation, in order to close the switch, the toggle member 28 is rocked in clockwise direction about its pivot 61 (Figure 2) thus tending to straighten the toggle composed of the members 24, 25 and the toggle composed of the members 28,29. This movement brings the bridge member 21 into contact with the fixed contacts 19, 20, overcoming the pressure. of the spring 23 and the toggles are retained in the position indicated in Figure 2 by the detent lever 33a pivoted at 34.

In the form illustrated, the actual operation of closing the switch is performed by a longitudinal movement of a tappet rod 1a brought about by rotation of a cam 52, a coin having been inserted in the slot 49 and. the handle 50 rotated. This mechanism,

however, forms no part of the present invention.

To efiect opening of the switch, the trip lever 33a is rocked in a clockwise direction about its pivot 84 by a pin 15 carried upon a wheel 13, thus tripping the end 33 of 5 the member 28 and allowing the spring 23 to thrust the'bridge member 21 away from V the contacts 19, 20. A spring 14 (Figure 2) assists in the breaking of the toggle 28, 29'. o a It is preferred that during closing of the M switch there should be a very slight lateral movement between the contact faces in order that self-cleaning of these contact faces may be effected. I 15 Owing tothe considerable area of the operative contact surfaces, any appreciable temperature. rise onopening the contacts is inhibited, and; furthermore, in conjunction with the considerable contact pressure applied by the toggle mechanism when the switch is closed, any appreciable local temperature rise whilst the switch is closed is also inhibited.

Switch mechanismas described above is V p adequate to control satisfactorily non-con- C3 tinuous current up to about 100 amperes. I hat is claimed is? "1. An electric switch including contact members having contacting surfaces, means for urging said surfaces into mutual con tact with sufficient pressure to prevent appreciable local temperature'rise whilst the switch is closed, means for causing said 7 surfaces to separate to extent of about .01 inch only to open said switch and means ensuring'that the contacting surfaces remain substantially parallel during. separation. i

a 2; An electric switch'as claimed in claim r 1 including a pair of fixed contact members H 0.;

and a mutually coacting movable bridge i member yielding a plurality of breaks in series upon opening of-the switch.

' 3. An electric switch as claimed in claim 1 wherein said means for urging together I V e V C3 the contacting surfaces comprise toggle mechanism.

4. An electric switch as claimed in claim 1 wherein said means for urging together the contacting surfaces comprise toggle mechanism actuated by further toggle mechanism.

In testimony whereof I have signed my name to this specification. 1

GERTRUDE RUTH ZIANI DE FERRANTI. I Legal representative of Sebastian Ziani De Ferranti,

Deceased. 

